Thanks for your help. I was trying your soltuion but I cant figure out the follwoing:
1. how I can view my output file? I don't see any generated output files
2. I assume "parser" in this case will be parsing the source file (where im getting my input from) right ?

I understand whats going on with your code but im just lost with where I see my results. I have tried multiple times but couldn't see any generated output file.
tried different examples using the same approach but still cant figure out how to get my output file.

how I can view my output file? I don't see any generated output files

You can print directly to a file using the toFile() method. Add the following lines to the example given above:

$new->addChild($features);
my $filename = 'new.xml';
my $ok = $new->toFile($filename,2);
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I assume "parser" in this case will be parsing the source file (where im getting my input from) right?

Yes, you would set up the parser like this, probably in a loop to go through each file:

my $file = 'file-1.xml';
my $parser = XML::LibXML->load_xml(location => $file);
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Thanks again for the help but unfortunately I only got the following in my output file when using $new->toFile('fileName')
<?xml version="1.0" encoding="utf-8"?>
I have tried this before reading your reply. But I got the same result. printing my results did help a bit just for debugging purposes. Also tried piping my print statements to a file but the formatting was not good and the text was from bottom to top
I just need to get this step done by seeing a nice formatted output so I can start playing around with the code and get what I want. Thanks again

I did actually include that line. You mean the same line you mentioned in your code in your first response right ?
I used your code exactly with tweaking few things like file names. The print is showing that its working overall but file output is unfortunately not
btw when I used your suggestion my $ok = $new->toFile($file-name,2) I got I/O invalid argument. I managed to get it work but as I said still doesn't show anything other than what I mentioned.
again thanks for your help

Here is my code:

use XML::LibXML;

my $parser = XML::LibXML->new();
my $doc = $parser->parse_file("FILE1.xml");

my @nodes_from_file1 = $doc->findnodes('//Feature');

my $new = XML::LibXML::Document->new('1.0', 'utf-8');

my $features = $new->createElement( 'Features' );

#print to debug 
print $features->toString;

my $file1 = $new->createElement( 'File1' );

for my $node (@nodes_from_file1) {
    $file1->addChild( $node );
    
    #print to debug
    print $file1->toString;
    
}
$features->addChild( $file1 );

print $new->toString;
$new->toFile("output_new.xml")
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I can't see the line $new->addChild($features);

You need to include the format argument 2 in $new->toFile("output_new.xml",2) and print $new->toString(2);

Thanks for your effort everything seem to be ok now. Just one last thing. The following is my current output.

<?xml version="1.0" encoding="utf-8"?>
<LINE Value="some_text">
  <status/>
  <FEATURES/>
  <File1_data>
    <ABC id="1">
    <Feature>
        <Number>im from file 1</Number>
        <Prefix>419</Prefix>
        <Alt>73924/</Alt>
    </Feature>
</ABC>
    <ABC id="2">
    <Feature>
        <Number>im from file 1</Number>
        <Prefix>826</Prefix>
        <Alt>27800</Alt>
    </Feature>
</ABC>
    <ABC id="3">
    <Feature>
        <Number>im from file 1</Number>
        <Prefix>827</Prefix>
        <Alt>26433</Alt>
    </Feature>
</ABC>
  </File1_data>
</LINE>
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as you can see that </ABC> (copied from Files_1 as a node) is not aligned properly so I just would like to learn how I can create nested elements and close them properly.
I have seen lots of examples but nothing is nested in the way I need it. I have tried many times but not sure whats going on. Following is what I need to get.

<?xml version="1.0" encoding="utf-8"?>
<LINE Value="some text">
  <status/>
  <FEATURES>
    <File1_data>
       <ABC id="1">
         <Feature>
           <Number>im from file 1</Number>
           <Prefix>419</Prefix>
           <Alt>73924/</Alt>
         </Feature>
       </ABC>
      <ABC id="2">
       <Feature>
          <Number>im from file 1</Number>
          <Prefix>826</Prefix>
          <Alt>27800</Alt>
       </Feature>
      </ABC>
     <ABC id="3">
      <Feature>
         <Number>im from file 1</Number>
         <Prefix>827</Prefix>
         <Alt>26433</Alt>
      </Feature>
     </ABC>
    </File1_data>
 </FEATURES>
</LINE>
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sorry for asking to much but any idea if I can access the elements Im copying and modify its name?
for example lets say I would like to add numbers to the Features elements im copying i.e <Feature 1> <Feature 2>....etc.